The world's first energy-saving lightbulb, made in 1976, has finally reached its maximum brightness. Switched on 37 years ago, the first 14 years passed without anyone realising it was emitting any light at all.

"All our initial calculations said we should have had some light straight away," Edward Hammer from General Electric said. "But in those early years we were left in the dark, quite literally. More recently, however, we have noticed light coming from the bulb and since then the future has been bright and it has now reached maximum power."

Technologies have moved forward since this early energy-saving bulb was invented. "We are now in the 21st century and expect bulbs to light up within the hour," Mr Hammer continued. "So now our next step is to invent a electricity-free light. Our best idea is a string-in-wax combination, but that sort of advanced engineering may be a few years away."